Process of evaporation and apparatus therefor.



P. KESTNER.

PROCESS OF EVAPORATION AND APPARATUS THEREFOR.

APPLICATION PILED AUG. 22, 1911.

Patented June 4, 1912;

ammo z Paul jfJZner PAUL KESTNER, or LILLE, FRANCE, ASSIG orPHILADELPHIA,

NORHIO KESTNER EVAPORATOR COMPANY, PENNSYLVANIA, A CORPORATION OFlENNSYLVANIA.

PROCESS OF EVAPORATION AND'APPARATUS THEREFOR.

- Application filed August 22, 1911.

a specification.

This invention relates to processes of evaporation and apparatustherefor; and it comprises a method of evaporation wherein liquid israpidly evaporated as a forced film which is .caused to ascend swiftlythrough evaporating tubes by contact with a stream of vapor, iscollected at the top dominant pool from which aregulated and adjustedvariable portion is constantly being returned to add to and enhance thevolume of inflowing fresh liquid and control the amount of liquidtemporarily in the apparatus whilethe residual excess of liquidaccumulating in said pool is taken to a point of discharge; and it alsocomprises an evaporator of the ascending film type provided witha.plurality of relatively long vertical tubes in a heating casing, withbasal feed means adapted to allow the formation of a'climbing film insuch tubes, with means for separating liquid and vapor in a surmountinghood casing and with means for allowing the accumulation of a body ofconcentrated liquid, said means being provided with a valved pipeleading back to the feed means and with an' overflow pipe leading to apoint of discharge; all as more fully hereinafter set forth and asclaimed.

In the evaporation of liquids it is found that, other things beingequal, the heattransmitting efficiency, that is, the evaporatingetliciency, of a heating surface depends largely upon the movementthereover of the liquid to be heated, or evaporated, the more rapid themovement of the liquid the greater being the efliciency. Thedesirability of movement and other reasons have led to the generalintroduction of filming evaporator-s in which the liquid is sentoverheated surfaces as a traveling film, or series of films; and therecognition of the still greater desirability of rapid movement hasbrought into use the climbing film type of evaporators in whichrelatively long heated vertiv cal tubes are basally fed with liquid, orwith liquid and vapor (it being advanta- Specification of LettersPatent.

' much more, rapid causes a rapid evaporation,

.movementand of evaporation may Patented June 4, 1912.

Serial No. 645,426.

geous, to use both) in such a manner that the liquid ascends through thetubes as an annular film carried onward and upward by the propulsiveinfluence of a central core or stream of onrushing vapor. As will bereadily apparent, since a given volume of liquid on evaporation becomesa very much greater volume of vapor, with evaporation going on in arelatively long vertical tube the forward .rush of vapor is, or may be,relatively violent and particularly where, as is usually the case, thevapor is withdrawn by exhausting or vacuum producing means. This rush ofvapor may be relied on to carry the liquid upward and forward as aforced film, the climbing film; a traveling 211111111 lus of liquidpassing over and thoroughly wetting the interior surfaces of the heatingtubes. Its movement forward is positive, since it is caused by thepropulsive effect of the swift vapor current, and is very rapid; thancan be attained where gravity alone is relied upon to cause travel as inolder forms of evaporators. And with this rapidity of movement is 0course correlated a corresponding efiiciency of heat transfer; and acorrespondingly rapid evaporation. The rapid movement giving a rapid andcopious evolution of vapors which, in the narrow tube, in turn causesthe rapid movement of liquid. This rapidity of lead to difliculties inpractical operation. \Vith a plurality of evaporating tubes operatingi'n parallel and fed by a common basal feed chamber, as in the usualtypes of apparatus, some tubes, unless special taken, may take the bulkof the liquid, transmitting liquid in thicker layers or annuli than aredesirable while other tubes may run 'dry, or with too little liquid.This may be largely obviated by proper distribution of incoming liquidin the feed chamber, an

by allowing self-evaporation in the chamber to form a cushion of steamor vapor surmounting the layer of liquid while providing the tubes withlaterally presented (as by beveling or slotting the ends), which shallsimultaneously tap both the steam layer and the liquid layer, ing asimultaneous even feed of both to each tube. But these expedients whileproviding for a uniform distribution of liquid among the several tubes,giving each its precautions are I or film over the whole evaporatingsurface of each tube from bottom to. top; something which isparticularly apt to happen in the case of a final eflect in a multipleeffect arrangement.

For a number of reasons, all the effects in a multiple effect apparatusare ordinarily of about the same dimensions; and present about the samearea of heating and evaporating surface to the liquid passingtheret-hrough. Now as the liquid travels serially through the successiveeffects and is concentrated as it goes, it is obvious that a largervolume of liquid is presented to the heating surfaces of the firsteffect than to those of the last; and the feed of liquid which may givean efficient thickness of fihn in the first effect may not in the last.Or in any effect,'with rapid operation the rate of inflow of liquidwhich at the bottom of the tubes will give an annulus ofefficientthickness, the lessened volume of liquid as it nears the top ofthe tube may cause the annulus to become converted into discrete streamsor runlets, leaving portions of the tube surfaces uncovered andconsequently not functioning in evaporation. These difficulties do notoccur, or do not occur to any such extent, in film evaporators in whichthe forward feed of the film is not forced but occurs naturally, as bygravitation; but they do obtain more'particularly with the forced rapidforward feed of the climbing films.

In the present invention, I obviate the noted difficulties and obtaincertain newadvantages in operation by making the amount of liquid: inthe climbing film effect, considered as a whole, at any given timeindependent of the temporary fluctuations of the feed or of theevaporation. To this end I provide what may be termed a dominant pool oraccumulation of concentrated liquid near the out-let from the system;and

from this accumulation I constantly withdraw adjusted and regulated butvariable and to this fresh liquid is added a proportions of liquid whichI return to the base of the effect to mingle with incoming fresh liquid,the excess of liquid over that necessary to form the accumulation andprovide the return being of course sent to dis charge as finishedliquid; finished, that is, so far as this particular effect is concernedthough it may of course go to another effect in series. In so operating,the effect is always being fed from a source of fresh liquid bulk-givingadjusted proportion of liquid which has already made a passage throughthe apparatus to give a total quantity of liquid from at the bottom ofthe pool.

the two sources which will uniformly cover the heating surfacesthroughout to the thickness desired. This allows me to force the forwardfeed of the film to make it travel as rapidly as may be desired and toforce the evaporation-without fear in so doing of causing inefficientdistribution among the several tubes or inefficient distribution of goodfilms throughout the extent of the inner or heating surface of thetubes.

The provision of an accumulation of concentrated liquid which maybeutilized as a dominant pool to aid in averaging out temporary tion, theoperator drawing back more or less as temporary exigencies; may demand,makes the operation of the-apparatus as a whole much more flexibleandcontrollable. The accumulation may be contained within the apparatusitself, or, and much more desirably, may be contained in a specialchamber. I In the operation of the climbing film vtype (if evaporator,it is customary to cause the liquid and vapor, which emerge jointly fromthe tops of the tubes with considerable speed and force, to be directedtangentially against the curved inner sur face of a surmounting vaporhood to form a whirling Wall of liquid from which the vapor separates bycentrifugal action. This whirling wall naturally slopes laterally andinwardly at the bottom; and the discharge pipe may be so arranged as togive an overflow into it at a point where the lateral slopingcontinuation has the desired depth to give the desired accumulation ofliquid while the valved pipe leading back to the feed chamber may tapthe .hoodchamber It is, however, much better'to discharge, all theliquid from the hood into a separate quieting chamber wherein the poolis formed and to connect the overflow pipe and the valved return pipe tothis chamber. In the hood the depth of the layer of liquid accumulatingdepends fluctuations of feed and, operanot only upon the amount ofliquid but upon the speed of whirl along the outer wall; and this speeddepends upon the temporary speed with which li uid' and vapor arp) beingdischarged from t e evaporating, tu es.

The tube leading back to the feed chamber should be valved-with areadily adjust able valve permitting quick, easy andclose adjustmentaccording to the temporary needs of the apparatus. It may usefully beprovided with a heating jacket; and in such event should have adepending-loop to facilitate circulation. This jacket may. receive steamor may receive vapor froma prior effect. It is also desirableto providethe feed pipebringing in fresh liquid with a heating Jacket, with, areserve tank and with a feedregulat-ing valve, j By regulating thevalves in the two pipes any relative proportions of preconcentrated andof fresh liquid may be admixed while the provision of the reserve tankmake the fresh liquid supply in a measure independent of thefluctuations in operation of a preceding effect.

In the accompanying illustration 1, have shown moreor lessdiagrammatically, apparatus within the present invention and adapted foruse in the stated process.

In this showing, Figure 1 is a view partly in section and partly inelevation, of a single effect; and Fig. 2 is a fragmentary similar viewof a modified form.

In Fig. 1, element 1 is a heating casing rovided with vapor inlet 2 andoutlet 3.

At the bottom of this casing cross header 4: separates it from feedchamber 5. \Vithin this feed chamber depend the ends of a plurality ofvertical evaporatingv tubes 6, each being relatively long and narrow. Asshown, these tubes are provided with depending prolongations 7 providedwith slotted or beveled (see 5*) ends to'give laterally presentedorifices which can tap both the steam space and the liquid space within.

the feed chamber. At their upper ends, the vertical evaporating tubesdischarge through conduits 8 having tangentially presented outlets orports. These outlets are within surmounting hood or vapor separatingcasing 9, which is advantageously of a generally circular section. Nearits top, the hood casing is provided with bat-wing separator 10 causingthe vapors to take a 'circuitous passage to vapor outlet 11. The violentstreams of vapor and liquid coming from the evaporating tubes aretangentially or angularly discharged against the inner wall of the hoodin such a manner as to make a whirling wall of liquid from which thevapor separates positively, bubbles being broken, etc. The whirling wall-"of liquid will have a centrally directed lateral slope which may reachnearl to or beyond the tangential outlets described. Tapping this bodyof liquid is a freely open outlet 12 leading the liquid to an overflowchamber 13. As shown, take-away pipe 14 extends 50 within this chamberto a sufficient height to give an overflow discharge. This take-awaypipe may lead to another effect or to a syrup tank, this depending uponthe arrangement of the etfect, whether it be an 5 intermediate effect ina series or the final effect. Tapping the bottom of this over- Howchamber is a conduit 15having valves.

16 and 16. As shown, this conduit has a depending loop .17 extending tothe feed chamber and a heating jacket 18'which may be supplied withvapor from a preceding eifect orwith steam as There may be adirectconnection with the feed chamber through a valved pipe 18. 5 Freshliquid is brought to the feed chamber the case may be."

by 19, coming from a source of juice or from a previous effect, as thecase may be. This conduit .is valved at 20 and is provided with gageglasses. 21 and 22. Intermediate the gage glasses, is shown a reservetank 23 which may be of any desired construction. The elements in Fig. 2are about the same save that the separate overflow tank is dispensedwith and the overflow pipe is continued upwardly within the hood casingwhile the return pipe taps the bottom of this casing. Diagrammaticallyshown liquid layer 24 gives the dominant pool.

As shown, 19 and 15 feed into opposite sides. of the supply chamber buttheymay enter at the same side. Any suitable deflecting means (notshown) may be used in the supply chamber to distribute inflowing liquidevenly in such chamber.

The operation of the device of Fig. 1 is obvious from the foregoing.

Liquid from a suitable source of supply passes into reserve tank 28whence adjusted amounts of the same may be admitted by opening valve 20into feed chamber 5 through 19.. At the same time, adjusted proportionsof liquid are returned from the overflow casing by opening valve 16.Heating jacket 18 allows the returned liquid to be heated. In devices ofthis character, it 5 is useful to have the liquid enter the feed chamberat a higher temperaturethan that which prevails in the effect; that is,than corresponds to the vacuum or pressure in such effect. In so doing,the entering liquid undergoes self-evaporation with the formation of asteam cushion and with the heating tubes having laterally presentedorifices at their base, both steam and liquid may be simultaneously fedupward through the tube. This much enhances the regularity of operation.As the liquid coming from the hood chamber is at the effect temperature,

it does not undergo self-evaporation in entering the feed chamber. Forthis reason,

the heating jacket 18 is useful. \Vith the heating jacket in use,depending loop 17 is useful as promoting circulation. I It is diflicultto induce liquid to flow downward through a heating jacket. The overflowpipe 14 passing upward some distance into 13 insures that a substantialpool or body of liquid shall remain in 13 at all times. Whatever thedemands on this concentrated liquid for returning purposes, caused bythe opening of valve 16, there will always be a substantial body ofliquid in 13 from which to tap. By opening or' closing valve 16 any.adjusted proportion of liquid from the-hood may be returned to the feedchamber at the base of the effect, while by similar control of 20adjusted proportions of freshliquid can be admixed therewith. Thereserve chamber 23 allows a flexible control of the 30 which is notpossible where the inlet for a mg conditions within said tube.

top of the tube and admixing the diverted amount of fresh liquidintroduced; a control I succeeding eli'ect communicates directly withthe outlet of a. preceding effect.

The heating jacket may .be supplied through valved pipe 25 with the samevapor or steam used in heating the effect, or with other vapor and steamfrom pipe 26, valved at 27.

hat I claim is c 1. The process of evaporating liquids which comprisespassing an inflowing body of liquid upward through a heated tube as anascending film, diverting a controlled amount of the liquid emergingfrom the top of ,the tube and admixing the diverted liquid with liquidfrom another source to form said body.

2. The process of evaporating liquids which comprises passing aninflowing body of liquid upward through a heated tube as an ascendingfilm, diverting a controlled amount of the liquid emerging from theliquid with liquid from another source to form said body, theproportionsof liquid so admixed being varied from time to time tocorrespond with 'variations in evaporat- 3. The process of evaporatingliquids which comprises passing an inflowing body of liquid upwardthrough a heated tube as an ascending film, collecting the liquidemerging from the top of the tube as a pool or body overflowing to apoint of discharge while diverting a controlled amount and admixing thediverted liquid with liquid from another source to. form said inflowingbody.

4. The process of evaporating liquids which comprises passing aninflowing body of liquid upward through a heated tube as an ascendingfilm, collecting the liquid emerging from the top of the tube as acomparatively quiescent pool or body overflowing to a point of dischargewhile di-' verting a controlled amount and admixing the diverted liquidwith liquid from another source to form said inflowing body.

5. The process of evaporating liquid an ascending film, collecting theliquid emerging from the top of the tube and diverting a controlledamount of it, reheating .the diverted liquid and admixing it with otherliquid to form said inflowing body.

6. In the operation of an ascending film evaporator, the process whichcomprises accumulating the liquid discharged from the top of evaporatoras a body, collecting another liquid as a body and feeding the base ofsaid evaporator with controlled proportions of the liquids of bothbodies.

.7. In an evaporating apparatus of the tubular ascending film type,means for iformv.

ing a pool or body of the liquid discharged at the top of the tubes,overflow discharge means and-a valved pipe connection leading back fromsaid pool to the base of the evaporator.

8. In an evaporating apparatus of the tubular ascending film type, meansfor forming a pool or body of the liquid dis charged. at the top of thetubes, overflow discharge means and a valved pipe connection leadingback from said pool to the base of the evaporator, said pipe connectionin eluding heating means.

9. An evaporating apparatus of the climbing film type, comprlsing aplurality of vertical evaporating tubes in a heating chamber, a hoodsurmounting such tubes, means for separating liquid and vapor andforming a body of liquid therein, a separate liquid receiving chamber inliquid communication with sald body, an overflow conduit leading awayfrom the liquid-receiving chamber, a supply chamber at the base of saidtubes, means for introducing fresh liquid to the same, and a valvedconnection between said separate liquid-rece1v1ng chamber and saidsupply chamber.

In testimony whereof, I aflix my slgnature in the presence or" twosubscribing witnesses.

PAUL KESTNER. Witnesses:

Leon PECKEL, V'lo'rou KLAUszMaNN.

